The following abbreviations may be used in this specification:
MSL Microstrip lines
CPW Coplanar waveguides
PCB Printed Circuits Board
MMW Millimeter-wave
SIW Substrate integrated waveguide
LCP Liquid-Crystal Polymer
TEM Transverse ElectroMagnetic
There a various frequency bands in use for transmitting data. More recently the MMW band has become more popular because of free usage and high-bandwidth.
Conventional transmission lines, such as MSL and CPW, are used widely in planar PCB circuits. However, for MMW, MSL and CPW may suffer from high loss and interference with each other due to radiation. On the other hand, traditional metal waveguides may have lower insertion loss for MMW and low radiation. Unfortunately, the transition from traditional metal waveguide to integrated planar circuits may be complex and the metal waveguide may be bulky in size.
In order to achieve very compact planar circuits in MMW frequencies, a SIW has been used instead of traditional metal rectangular waveguides. Examples include MMW packaging, MMW SIW antennas and SIW filters.